Central Air-Conditioning Relay Control for Overheat Shutdown
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Solution Overview
Problem
Air-conditioning control apparatuses using latching relays face issues with contact sticking due to arcs and degradation, leading to unintended continuous operation of air-conditioning units, which can result in abnormally high room temperatures and failure to stop the operation when contact states are terminated or power supply is interrupted.
Innovation Solution
Incorporating a microcomputer that controls the output of alternating-current voltage to the air-conditioning unit, using a protective opening/closing unit to manage power supply paths and a temperature detection system to stop the heating operation when a predetermined temperature is reached, ensuring the air-conditioning unit is stopped before the room temperature becomes excessively high.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a latching relay is used to control the air-conditioning unit, then heat generation is reduced and temperature measurement accuracy is improved, but contact sticking occurs due to arcs and degradation leading to unreliable operation termination
Solution Approach 1:
A protective opening/closing unit is introduced as an intermediary component between the latching relay and the air-conditioning unit. This unit includes a relay that opens/closes based on temperature detection results, acting as a safety mediator to terminate power supply when abnormal temperature is detected, thereby preventing contact sticking from causing harmful effects
Solution Approach 2:
The patent replaces the purely mechanical latching relay contact control with a hybrid system that incorporates electronic temperature detection and control circuitry. The microcomputer-based temperature detection system substitutes for manual monitoring, enabling automated safety intervention when temperature thresholds are exceeded
2Duration of action of stationary object
If the latching relay contact sticks in the closed state, then the air-conditioning unit continues operating, but the room temperature becomes abnormally high creating harmful effects
Solution Approach 1:
The protective opening/closing unit performs preliminary action by continuously monitoring temperature and preparing to terminate operation before harmful effects occur. When temperature reaches a predetermined threshold, the system proactively opens the relay to cut power supply, preventing the air-conditioning unit from continuing operation under faulty conditions that would cause abnormally high temperatures
Solution Approach 2:
A temperature feedback mechanism is implemented where the temperature detection unit continuously monitors room temperature and feeds this information back to the control circuit. This feedback loop enables the system to detect abnormal temperature conditions and automatically trigger the protective opening/closing unit to terminate operation, preventing harmful overheating
3Use of energy by moving object
If power supply to the control system is stopped, then energy consumption is reduced, but the latching relay contact state cannot be terminated leading to loss of control
Solution Approach 1:
The protective opening/closing unit is designed to function autonomously when temperature abnormalities are detected. The temperature detection unit automatically triggers the relay opening without requiring continuous power to the main control system, enabling the system to self-terminate operation even when power supply is interrupted, thus maintaining control termination capability while reducing energy consumption
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures the air-conditioning unit is reliably stopped before reaching an abnormally high temperature, preventing overheating and allowing for accurate temperature control, even when contact sticking or power supply issues occur.
Implementation Method 1
a temperature detection unit that detects the room temperature
Implementation Method 2
When the supply of power supply voltage is stopped, the air-conditioner stops the operation
Data Source
AI summary
An air-conditioning control apparatus controls an air-conditioning unit used in a central air-conditioning system that conditions a plurality of rooms in a house by a single air-conditioning unit. In the apparatus, a microcomputer starts an output of an ON command signal when started, subsequently continues the output of the ON command signal when a detected temperature inside a room is lower than a predetermined determination temperature, and stop the output of the ON command signal when the detected temperature is equal to or higher than the predetermined determination temperature. A protective opening and closing unit closes a first power supply path between a voltage input terminal and an internal alternating-current power supply line when the ON command signal outputted from the microcomputer is supplied, and opens the first power supply path when the supply of the ON command signal is stopped.